Embodiments of the present invention relates to a blade device and an X-ray imaging apparatus. Particularly, embodiments of the present invention are concerned with a blade device comprising four blade members to form a hollow cone having both open ends, as well as an X-ray imaging apparatus having the blade device.
An X-ray imaging apparatus has a collimator for adjusting an irradiation field. On an inlet side of the collimator there is disposed a blade device for excluding an off-focal radiation, i.e., X-ray radiated from outside an X-ray focal point.
In the blade device, a hollow cone having both open ends is formed using four X-ray impermeable blade members. The tip of the cone is directed to an X-ray focal point lest X-ray radiated from outside the X-ray focal point should get into the collimator.
The blade device is constructed such that the shape of the cone is adjusted in interlock with the irradiation field adjustment performed by the collimator to always permit optimal exclusion of an off-focal radiation irrespective of whether the irradiation field is large or small (see, for example, column 7 line 66 to column 9 line 19, FIG. 6, FIG. 7, of U.S. Pat. No. 4,246,488).